For sensing the vehicle's front axle height position, angle sensors integrated in ball joints have been developed. These are, as compared to commonly used height position sensors, distinctly more robust, produce a better signal quality, and are more cost efficient. For the vehicle's rear axle, in most vehicles ball joints are uncommon, methods for measuring the height distance, residing in a rubber bearing, have been to developed in the past. These measurement methods, however, have several disadvantages. For instance, the bearing's rubber enclosure needs to have magnets inserted into it, which results in the enlargement of the bearing's size. In addition, additional costs will occur, due to the use of the plastic enclosed magnets, special applied magnetizing, magnet sensitive sensors, external amplifiers and controllers, as compared to using angle sensors inside the ball joint.
Through DE 102 21 873 A1, a rubber bearing with a deflection sensor is known, which comprises an inner ring, an outer ring, and has arranged in between these a rubber ring. At the outer ring, a Hall-Sensor is attached through a bracket, placed between two magnets, and which is attached to the inner ring by way of a mounting part. When the inner ring turns in relation to the outer ring, which correlates to either a deflection or a hopping, the Hall-Sensor moves towards either the left or right magnet, whereby the Hall-Sensor's surrounding magnetic field changes. The change of the magnetic field is then detected by a following electronic circuit.
The EP 1 707 922 A1 describes a sleeve bearing with an outside bushing, an inner bushing and, positioned in between these is an elastomeric body. The elastomeric body is a two-part unit, with a permanent magnet and a galvano magnetic sensor positioned in the gap between the two elastomeric body parts, magnetically connected in series and rigidly linked with the inner bushing. In addition, the gap contains a magnetically conducting ring which surrounds the magnetic series connection and is placed in such a way, that an air gap exists on both sides. The shape of the ring is such that an outer bushing's torsion, in relationship to the inner bushing, will create a change of the air gap's length. By means of a sleeve bearing, a suspension arm with the associated wheel is pivotally connected to the vehicle's body.
The disadvantage of this design is the need to insert magnets and or sensors into the bearing's rubber material, which results in the enlargement of the needed space of the actual bearing and, by comparison, a more sophisticated manufacturing.
In addition, DE 44 29 856 C1 discloses a vehicle's wheel suspension, comprising a body, a wheel, at least one suspension arm, through which the wheel is connected to the body, a bearing, through which the suspension arm can be pivoted at least in one axis at the body, at which a bearing's inner part is mounted. Also, an angle measuring device is present, through which pivoting of the suspension arm's pivot axle, relative to the body, can be measured. The angle measuring device comprises a component, designed as a signal generator (6a), and a component serving as a sensor. The angle measuring device, including the signal generator and sensor, are mounted on the suspension arm's side, which not only causes the configuration to be unfavorably wider, but it also requires that an additional, external leaf spring component, for driving and clamping the sensor.